1. Swiss Federal Institute for Forest Snow and Landscape Research WSL Zürcherstrasse 111 CH‐8903 Birmensdorf Switzerland
2. Forest Ecology Department of Environmental Systems Science ETH Zürich CH‐8092 Zürich Switzerland
3. INRA UMR 1391 ISPA 71 l'Avenue Edouard Bourlaux 33140 Villenave d'Ornon France